Black powder finds considerable use for ignition of smokeless powder, time fuzes, squibs, rocket propulsion units, etc. It is no longer employed as a military propellant. Standard black powder contains 74.0 .+-. 1% KNO.sub.3, 15.6 .+-. 1% charcoal and 10.4 .+-. 1% sulfur.
In the manufacture of black powder, as conventionally practiced, charcoal and sulfur are pulverized together in a wheel mill, whereby some of the sulfur is incorporated into the pores of the charcoal. In view of the danger of explosion the potassium nitrate is ground separately in the wheel mill. The pulverized mixture of sulfur and charcoal is moistened, mixed with the nitrate and milled in a wheel mill, whereby the degree of incorporation is increased. The milled material is then pressed into cakes in a hydraulic press, and the cakes are broken up in a corning mill having adjustable rolls with corrugated surfaces, which reduce the material to the desired grain size. The product from the corning mill is screened to remove fines, which are returned to the wheel mill, and the coarse granules are passed through the corning mill a second time and then rescreened. The resulting granules are blended by tumbling in a rotating hardwood drum, wherein the powder is heated by friction to as much as 65.degree.C. and any moisture is removed by evaporation. Since it is generally desired to glaze the powder, graphite is added to the contents of the drum before the powder is too dry. The dried powder is then screened into standard granulations.
Although the foregoing operations have optimized the manufacture of black powder, they are nonetheless time-consuming and hazardous, and require special types of apparatus. Recently, it has been proposed according to U.S. Pat. No. 3,660,546 to prepare meal black powder by simultaneously effecting the mixing, pulverizing and grinding of the sulfur, carbon and potassium nitrate by continuous introduction thereof into a jet mill, wherein air tangentially introduced under high pressure subdivides the particles by striking each other. The resulting powder is further processed by pressing into cakes, disintegration, screening, blending, etc., to produce standard black powder granules.